Obama’s pushing hard against reasonable immigration reform/enforcement combined with RadioE/conservative punditry/organizations were the driving force behind the Gang of Eight legislation as well as Romney’s self deport option.
IMO Obama’s reasoning was because he needed something major to distract from Obamacare’s failing as predicted. The opposition have always been there with stories of illegals invading, many of them true. The aggregation of stories combined with Obama’s lawlessness on the issue created an environment that caused Obamacare to be ignored as an issue in this election.
Noted: Marco Rubio’s successful , forceful and at times almost solo push against the risk corridors should (IMO) have been a winning issue for him.
Further note: I don’t think Trump’s very public and extreme solutions to illegal immigration were incidental to Obamacare being almost abandoned as a campaign issue so soon after opposition to it being a core principle. He is decidedly to the left of center on health care.